The Most Interesting Things I've Learned in High School

In my senior english class, we are suppose to compose a post about some of the most interesting things I've learned in high school. When I think about it, high school has gone by really fast, but at the same time I have taken a lot of classes and learned a lot in this short period of time.
I think one of the most interesting classes I took was AP Psychology sophomore year. I think it is fascinating how the brain works, and how it sometimes plays tricks on people. My favorite unit was on how exercise affects the brain. I love to run, and it was interesting to learn about what chemical reactions happen in the brain when you exercise. It improves memory, cognitive attention span, and overall health of your brain. Exercising before studying for a big test can help retention, and exercising before the actual test can help you perform better.
Last year, my favorite class was AP Biology. I find biology really interesting, especially the unit on cells. One topic I found very interesting was apoptosis. It is the programed cellular death. Certain cells have genes that purposes trigger the cell to kill itself. It is used to form fingers during development. You first grow a "paddle" where your hand is, and the cells in between your fingers go through apoptosis and die. Symbiosis was also an interesting topic. When I went to an ecosystem with my teacher for a project, we found a root that "lets" a certain bacteria live inside of it, because the bacteria will perform nitrogen fixation for the root in return. They have an "agreement" of sorts, where the root offers protection and the bacteria offers nitrogen fixation in return.
This year, I am taking AP Government & Comparative Politics and I find it really interesting; especially comparing different countries. Its interesting to learn about how Russia and Nigeria have elections, but there is heavy fraud in them. Iran is a theocracy where both the Assembly of Religious Leaders and the Guardian Council are groups of Islamic leaders that are part of the government. And Britain is the closest to the United States but there is much more class division and party-line voting than in America.
Aside from the major concepts in the school curriculum, there are, of course, those random facts you learn along the way. In health I remember we learned that people lose on average 100 hairs a day., cold weather makes fingernails grow faster, and a person eats the equivalent of about 6 elephants by the end of their life.